Integrated circuits routinely include components that are formed closely together. For example, bipolar transistors and other types of transistors are often fabricated next to each other on a substrate. The formation of transistors close to one another can often lead to problems, such as when the structure of one transistor overlaps or collides with the structure of another transistor.
To avoid problems such as this, trenches are often formed between transistors or other components in an integrated circuit. For example, a trench can be formed in a substrate between two transistors before the transistors are formed. The trench helps to separate the areas of the substrate where the two transistors are being formed.
There are several different types of trenches used in integrated circuits. Deep trench isolation (DTI) typically refers to a process for forming deeper, narrower trenches in a substrate. Shallow trench isolation (STI) typically refers to a process for forming shallower, wider trenches in a substrate. It is also possible to combine the two processes, such as by forming a shorter, wider trench over a deeper, narrower trench in a substrate. In this technique, both the deeper trench and the narrower trench are simultaneously filled with one or more materials, such as an oxide.